As shown in Figure 1, a polar-ring
galaxy can be difficult to
distinguish when viewed from certain projection angles, and can look
like a fairly normal galaxy (i.e., an edge-on spiral galaxy with an
abnormally spherical bulge, or a barred galaxy with ring-like arms).
Category B includes systems that are oriented in such a way that we
can be fairly sure the system is actually a polar-ring galaxy based on
morphological appearance, but kinematic observations have not yet been
made to confirm the classification.

The projected major axis of the two components must be nearly
orthogonal.

The centers of the two components must be nearly aligned.

The ring must be comparable in size to the inner component, must be
luminous, and it must be nearly planar.